When operating an electronic circuit breaker it is highly desirable that any functions performed to upgrade the software or firmware of the breaker's microcontroller be accomplished without interruption and without sacrificing protection of the load. In a traditional electronic circuit breaker, once tripped, the microcontroller controlling the breaker has no power and is inaccessible. Thus, in past known electronic circuit breakers the microcontroller state is on or off, mirroring the closed or open position, respectively, of the breaker contacts.
To perform a firmware upgrade, the breaker either needs to 1) be removed from the load center, or 2) perform fault protection during the upgrade process, or 3) enter a mode of operation where fault protection is not required. With respect to 1), removing the breaker from the load center is not ideal for firmware upgrades in terms of maintenance time and wear on the breakers and associated equipment, as well as the safety aspects of breaker removal. With respect to 2) there is microprocessor overhead required to provide fault protection during the upgrade process or determining if the breaker can enter a mode of operation where fault protection is not required. One example of updating the firmware while providing protection requires two separate program sections and a separate boot section. To ensure protection is uncompromised, the new program would have to be written into a separate section of memory while the existing program continues to detect for fault protection. Then, once the new program is validated, the processor would have to do a reset, and the boot section of the microcontroller would have to track which firmware program to use in the future in order to always point to the newest program. Additional processor overhead is required to handle the case when a fault is detected, and the new program is being written to the program section to ensure the breaker can't enter a hazardous mode of operation.
Today's residential electronic circuit breakers (AFCI) monitor and protect against many different types of fault conditions. When a circuit breaker trips, it is advantageous to know what type of fault the circuit breaker interrupted in order to accurately and rapidly correct the fault condition. The electronic modules in such circuit breakers are capable of indicating the interrupted fault only when the electronics are powered. Normally this requires re-closing the circuit breaker with its manual handle to power the electronic module. However, re-closing the circuit breaker to indicate the cause of the interrupted fault also means re-energizing the fault if the fault is still present. In order to safely re-close the circuit breaker, an electrician must open the load center and remove the line load and neutral load wires from the circuit breaker. It would be desirable to have a secondary means of powering the electronic module to allow the electronic module to indicate the interrupted fault, without the need to re-energize the fault at levels that would be considered hazardous, thus eliminating the need to remove the load wires from the circuit breaker.